Read title.

It's all timing; you just get a feel for it. You have to jump while on the springs at a specific time.

Do you mean how high you jump? Depending on how late you press the jump button on those spring platform determines how high you go, so you want to jump as late as possible on them to go super high.

Pressing it too late won't give you any extra height, though.

I'd say to hold the up key around the same time you start going up. If you hold it too early, you'll go even lower than you would normal

You’ll eventually get a feel for when to jump, it took me a while to first get the timing right, but I would say your best bet is to try about when the ball is getting into the air